For example, known ceiling-mounted air conditioners include the type that each of both long-side lateral ends of a rectangular interior panel has a couple of air inlet and air outlet juxtaposed to each other (see, for example, Patent Document 1). The interior panel of the air conditioner of this type is formed to bring a rectangular frame and a flat center plate into flush with each other. Four elongated openings are disposed between the frame and the center plate, two in each of both long-side lateral ends of the interior panel. Out of these openings, two located towards the center of the panel are air inlets and two located towards the outside of the panel are air outlets.    Patent Document 1: Japanese Patent Publication No. 2988329